Sustainable agriculture is a long-term approach that combines efficient production with wise stewardship of the earth's resources. Sustainable agriculture includes developing environmentally benign production techniques. One such method involves the development of transgenic crops that incorporate genes that product toxic gene products, or proteins targeting a specific pest larval form. Incorporating the gene into plants eliminates or vastly reduces the amount of traditional pesticides that must be used on crops. The most serious threat to the efficacy of transgenic plants is the evolution of resistance to expressed toxins by insect pests.
Transgenic plants that produce insecticidal substances, however, should be subject to careful testing to ensure human safety and to minimize adverse environmental impacts. Potential environmental impacts unique to transgenic plants include transfer (by cross-pollination) of the new insecticidal gene to wild or weedy relatives of the transgenic crop, as well as the establishment of self-seeded or vegetative propagated crops such as weed in either managed or natural habitats.
The United States Environmental Protection Agency considers preservation of susceptibility to transgenic toxins to be in the public interest, and proteins such as those produced by Bacillus thuringienses are therefore worthy of extra protection (U.S. Environmental Protection Agency and U.S. Department of Agriculture, 1999). Insect resistance management (IRM) relates to practices aimed at reducing the potential for insect pests to become resistant to a pesticide or transgenic plant. IRM is important for transgenic crops, particularly for those crops expressing Bacillus thuringienses proteins (commonly called Bt crops), because insect resistance poses a threat to the future use of microbial Bt formulation in organic farming and Bt technology as a whole. Scientists, public interest groups, and organic growers and other farmers have expressed concern that the widespread planting of such genetically modified plants will hasten insect resistance to Bt endotoxins, as well as to other toxins produced by transgenic plants.
Under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the U.S. Environmental Protection Agency requirements for transgenic crop registration are designed to ensure that there will be no unreasonable, adverse effects from the use of a pesticide when economic factors are fully considered. With the application of Bt technology, the EPA has stated that it is working to prevent what would happen if Bt no longer could control insect pests, and more toxic insecticides had to be used in its place. In 2000 the EPA imposed new IRM requirements on registered transgenic crops to combat insect resistance to Bt endotoxins. Sound IRM will prolong the life of transgenic insecticides, and adherence to IRM plans benefits growers, producers, researchers, and consumers.
The U.S. EPA has required seed producers to formulate a program of crop stewardship to include an active crop monitoring program and the adoption of an insect resistance management program as part of registration for transgenic crops that produce an insecticide protein. For example, field corn is a crop in which genes for insecticidal proteins have been inserted to protect against both the European corn borer and the corn rootworm.
The current monitoring program is a shared activity across the industry. This monitoring program is based on sampling for resistant insects during the crop season in four discrete areas that are considered to be potential areas of concern. The insects collected are subjected to a dose-response assay to detect if any of the larvae are resistant to the toxin expressed in the crop plant. The IRM program involves the insecticide protein coupled with a refuge of non-transgenic plant hybrids.
Current EPA resistance management for Bt corn hybrids for European corn borer is 20% of the corn acreage plants to a non-Bt corn hybrid of similar maturity within one half mile of the Bt-corn field. It is recommended that the hybrids be planted at approximately the same date as the transgenic crops. EPA requirements for Bt-corn hybrids for corn rootworm is much the same, with the modification that the refuge must be within the same filed or in an adjacent field. A one half mile distance is not permitted.
The refuge requirement is a legal requirement for companies marketing Bt-corn hybrid. The seed technology companies with the registration are responsible for assuring that framers planting their hybrids meet compliance standards. Failure to meet these standards can result in a company losing its registration or right to sell the hybrids within an area where a significant number of farmers are out of compliance with refuge management regulations.
Although implementation of refuge areas in a resistance management program is a legal requirement, policing the regulation is a formidable task. For this reason, remote sensing technology is considered to be the best method of obtaining a general view of the degree of compliance across large geographic areas and within high adoption areas.
Presently, monitoring of transgenic corn acreage for development of pest resistance rests on the collection of viable pest samples from four specific areas in the U.S. corn belt. There have been concerns that the seed industry is unable to report information about resistance outbreaks in a timely fashion. Since resistance development has been seen to be a “local” phenomenon, the course scale of the sampling used in current monitoring programs could easily miss areas or development of resistance.
The landmass of more than 25 million acres of transgenic corn alone does not permit the level of scrutiny to properly identify resistance development economically at an acre by acre level of inspection.
It is also useful to monitor groups of plants or areas of agricultural or other types of growth for conditions of the plants, such as response to physiological stress, insect infestation, and the like.